Effect of combined high temperature and tensile load on the post-fire performance of high-strength steel

• Post-fire response of S700 under temperature and tensile load has been evaluated. • The test setup was designed to closely simulate real fire and post-fire scenarios. • Steel grade and production route affect post-fire behaviour more than load. An experimental campaign to evaluate the post-fire performance of grade S700 steel specimens subjected to a range of temperatures between 300°C and 1000°C and simultaneous tensile load, followed by natural cooling to room temperature, has been undertaken and is presented herein. The adopted test procedure provides a close representation of real fire and post-fire scenarios, since during a fire a structure is also subjected to a certain load level, an aspect that is usually neglected in research on this topic. The residual values of the key mechanical properties, including the yield strength, ultimate strength, Young’s modulus, strain at fracture and ultimate strain, were computed. According to the experimental results, the post-fire response was found to be dependent on the production route of the tested material and, under some combinations of temperature and tensile load, the residual values of ultimate strain did not meet the Eurocode 3 ductility requirements, indicating that the residual ductility of a steel structure surviving a fire could be compromised. The present work provides valuable data for the safety assessment of structures after fires, and aids decision-making on whether to re-use, retrofit or demolish.